HP OpenVMS DCL Dictionary
Closes a mounted disk or tape volume for further processing and deletes
the logical name associated with the device.
Requires the GRPNAM (group logical name) and SYSNAM (system
logical name) privileges to dismount group and system volumes.
Name of the device containing the volume---either a logical name or a
physical name. If a physical name is specified, the controller defaults
to A and the unit defaults to 0.
If the volume currently mounted on the device is a member of a disk or
tape volume set, all volumes in the set are dismounted, unless the
/UNIT qualifier is specified.
The DISMOUNT command (which invokes the $DISMOU system service) checks
for conditions that prevent a Files-11 volume from dismounting. The
conditions fall into the following categories:
- Installed swap and page files
- Installed images
- Devices spooled to the volume
- Open user files (any files not falling into one of the first three
If the DISMOUNT command does not find any of these conditions, it
performs the following operations:
- Removes the volume from the user's list of mounted volumes, deletes
the logical name (if any) associated with the volume, and decrements
the mount count.
- If the mount count equals zero after being decremented, the
DISMOUNT command marks the volume for dismounting.
As soon as the
volume is idle, that is, after the DISMOUNT command has determined that
no user has any open files on the volume, the DISMOUNT command marks a
Files-11 volume for dismounting, and dismounts the volume soon.
- If the mount count does not equal zero after being decremented, the
DISMOUNT command does not mark the volume for dismount (because the
volume must have been mounted shared). In this case, the total effect
for the issuing process is that the process is denied access to the
volume and the logical name is deleted.
- After a volume is dismounted, nonpaged pool is returned to the
system. Paged pool is also returned if the volume was mounted using the
/GROUP or /SYSTEM qualifiers.
If the DISMOUNT command does find open files or any other condition
that prevents the volume from dismounting, it does not mark
the volume for dismounting. Instead, the DISMOUNT command displays a
message indicating that the volume cannot be dismounted, followed by
messages indicating the conditions that exist and the number of
instances of each condition.
The /OVERRIDE=CHECKS qualifier allows a volume to be marked for
dismounting despite open files or other conditions. For example,
marking a volume for dismounting prevents any new files from being
opened. Also, when a volume is marked for dismounting, file-system
caches are flushed. This activity is especially important when the
system is shutting down and the file-system caches must be written to
If a volume is part of a Files-11 volume set and the /UNIT qualifier is
not specified, the entire volume set will be dismounted.
If the volume was mounted with the /SHARE qualifier, it is not actually
dismounted until all users who mounted it dismount it or log out;
however, the DISMOUNT command deletes the logical name associated with
If the device was allocated with an ALLOCATE command, it remains
allocated after the volume is dismounted with the DISMOUNT command. If
the device was implicitly allocated by the MOUNT command, the DISMOUNT
command deallocates it.
If the volume was mounted with the /GROUP or the /SYSTEM qualifier, it
is dismounted even if other users are currently accessing it. The
GRPNAM and SYSNAM user privileges are required to dismount group and
system volumes, respectively.
Requires volume ownership or the user privilege VOLPRO (volume
protection) to use this qualifier with a volume that was mounted with
neither the /GROUP nor the /SYSTEM qualifier. Additionally requires the
user privilege SHARE if the volume is mounted privately by a process
other than the process issuing the DISMOUNT command.
Specifies that the volume is to be dismounted, regardless of who
mounted it. The primary purpose of the /ABORT qualifier is to terminate
mount verification. The DISMOUNT/ABORT command also cancels any
outstanding I/O requests. If the volume was mounted with the /SHARE
qualifier, the /ABORT qualifier causes the volume to be dismounted for
all of the users who mounted it.
Dismounts a volume throughout a mixed-architecture OpenVMS Cluster
system. If you specify DISMOUNT/CLUSTER, the DISMOUNT command checks
for open files or other conditions that will prevent a Files-11 volume
on the local node from dismounting. If the DISMOUNT command does not
find any open files or other conditions, it checks for conditions on
all other nodes in the OpenVMS Cluster. If the DISMOUNT command finds
one of the conditions on any node, it displays an error message
identifying the device and the nodes on which the error occurred,
followed by an error message indicating open files or other conditions
on the volume.
After the DISMOUNT command successfully dismounts the volume on the
local node, it dismounts the volume on every other node in the existing
OpenVMS Cluster environment. If the system is not a member of a
cluster, the /CLUSTER qualifier has no effect.
Expels a named shadow set member from the shadow set.
If connectivity to a device has been lost and the shadow set is in
mount verification, you can use the
to immediately expel a named shadow set member (ddcu:) from
the shadow set. If you omit this qualifier, the device is not
dismounted until mount verification completes.
Note that you cannot use this qualifier in conjunction with the
/POLICY=MINICOPY (=OPTIONAL) qualifier.
The device specified must be a member of a shadow set that is mounted
on the node where the command is issued.
Marks a Files-11 volume for dismounting even if files are open on the
volume. If you specify DISMOUNT/OVERRIDE=CHECKS, the DISMOUNT command
displays messages indicating any open files or other conditions that
prevent dismounting, immediately followed by a message indicating that
the volume has been marked for dismounting.
This command does not close open files on the device. A device cannot
be properly dismounted until either all processes with open files have
properly closed them, or the processes have been rundown completely.
A substantial amount of time can pass between the time you enter the
DISMOUNT/OVERRIDE=CHECKS command and the completion of the dismount
operation. Always wait for the dismount to complete before you remove
the volume. (To verify that the dismount has completed, enter the SHOW
DEVICES command.) Note that the final phase of volume dismounting
occurs in the file system, and all open files on the volume must be
closed before the actual dismount can be done. Note also that the file
system cannot dismount a volume while any known file lists associated
with it contain entries.
By using this command, the device is marked for dismount. This prevents
additional processes from opening files on the device while existing
open files are closed.
/POLICY=[NO]MINICOPY[=(OPTIONAL)] (Alpha/I64 only)
Controls the setup and use of the shadowing minicopy function.
Requires LOG_IO (logical I/O) privilege to create
The exact meaning of the MINICOPY keyword depends on the context of the
DISMOUNT command, as follows:
- If this is a dismount of a single member from a multi-member shadow
set, a write bitmap is created to track all writes to the shadow set.
This write bitmap may be used at a later time to return the removed
member to the shadow set with a minicopy.
If the write bitmap
cannot be initiated and the keyword OPTIONAL is not specified, the
dismount will fail and the member will not be removed.
you omit the /POLICY qualifier or if you specify /POLICY=NOMINICOPY, no
bitmap will be created.
- If this is the final dismount of the shadow set in the cluster, the
shadow set is verified to be capable of a future minicopy operation.
If the shadow set has only one member or is in a merge state, and
if OPTIONAL was not specified, the dismount will fail.
neither NOMINICOPY nor MINICOPY is the same as MINICOPY=OPTIONAL, as
the set will be dismounted regardless of the prior checks.
For additional information, refer to HP Volume Shadowing for OpenVMS.
Dismounts only one volume of a volume set on the specified device. By
default, all volumes in a set are dismounted.
Avoid dismounting the root volume of a volume set, because it contains
the master file directory (MFD). It may be impossible to access files
on a volume set if the MFD is not accessible.
Determines whether the device on which the volume is mounted is
physically unloaded. If you specify the DISMOUNT command without the
/UNLOAD or the /NOUNLOAD qualifier, the qualifier that you specified
with the MOUNT command (either /UNLOAD or /NOUNLOAD) determines whether
the volume is unloaded physically.
$ MOUNT MTA0: PAYVOL TAPE
$ DISMOUNT TAPE
The MOUNT command in this example mounts the tape whose volume
identification is PAYVOL on the device MTA0: and assigns the logical
name TAPE to the device. By default, the volume is not shareable. The
DISMOUNT command releases access to the volume, deallocates the device,
and deletes the logical name TAPE.
$ MOUNT/SHARE DKA3: DOC_FILES
$ DISMOUNT DKA3:
The MOUNT command in this example mounts the volume labeled DOC_FILES
on the device DKA3. Other users can enter MOUNT commands to access the
device. The DISMOUNT command shown in this example deaccesses the
device for the process issuing the command. If other users still have
access to the volume, the volume remains mounted for their process or
$ DISMOUNT/NOUNLOAD DMA2:
The DISMOUNT command in this example dismounts the volume; the
/NOUNLOAD qualifier requests that the volume remain in a ready state.
$ MOUNT/BIND=PAYROLL DMA1:,DMA2: PAYROLL01,PAYROLL02
$ DISMOUNT/UNIT DMA2:
The MOUNT command in this example mounts PAYROLL, a two-volume set. The
DISMOUNT command dismounts only PAYROLL02, leaving PAYROLL01
accessible. Note that because the master file directory (MFD) for the
volume set is on the root volume, you should not dismount the root
volume (in this case, PAYROLL01) of the volume set.
$ DISMOUNT $10$DJA100
%DISM-W-CANNOTDMT, $10$DJA100: cannot be dismounted
%DISM-W-INSWPGFIL, 4 swap or page files installed on volume
%DISM-W-SPOOLEDEV, 3 devices spooled to volume
%DISM-W-INSTIMAGE, 7 images installed on volume
%DISM-W-USERFILES, 6 user files open on volume
The DISMOUNT command in this example displays the open files and other
conditions that prevent device $10$DJA100 from dismounting.
$ DISMOUNT/CLUSTER $10$DJA100
%DISM-W-RMTDMTFAIL, $10$DJA100: failed to dismount on node SALT
%DISM-W-FILESOPEN, volume has files open on remote node
%DISM-W-RMTDMTFAIL, $10$DJA100: failed to dismount on node PEPPER
%DISM-W-FILESOPEN, volume has files open on remote node
%DISM-W-CANNOTDMT, $10$DJA100: cannot be dismounted
The DISMOUNT command in this example displays messages identifying
device $10$DJA100 and nodes SALT and PEPPER on which errors occurred
followed by messages indicating open files on the volume.